Method and apparatus for manufacturing marked articles to be included in cans

ABSTRACT

In a method and apparatus for manufacturing articles (e.g., opening tabs) to be included in cans, a metal strip is fed into an article forming unit in which the metal strip is punched and stamped to form the articles. Before the article forming operation, the strip is provided with laser engravings on at least one of its upper and lower surfaces. The laser engravings are provided on the strip when the strip is in an immobilized condition.

This is a continuation of International Application No. PCT/SE99/00692,filed on Apr. 28, 1999, claiming priority from Swedish patentapplication No. 9801489-7, filed on Apr. 28, 1998.

TECHNICAL FIELD

The present invention generally concerns the technique of manufacturingarticles to be included in cans, in particular beverage cans. Theinvention is specifically, but not exclusively, related to articles inthe form of opening tabs to be attached to shells for forming ends tosuch cans.

BACKGROUND ART

In a brochure entitled “This is PLM Fosie” issued by Applicant's Swedishcompany PLM Fosie AB in the mid nineties, there is shown on p. 6 how canends are produced.

In a first production stage, a thin metal strip, preferably a0.23-mm-thick aluminium strip, is fed to a tab forming unit in which thestrip is punched and stamped to form opening tabs integrated with thestrip. The tabs are also referred to as opener rings by persons skilledin the art.

In a second production stage, circular shells for forming the can endsare die cut from a thin metal sheet, preferably a 0.23-mm-thickaluminium sheet. Each shell is scored for opening, and a rivet forattachment of the tab is formed at the centre of the shell.

In a third production stage, the strip with the integrated tabs arejoined with the circular shells in an attachment station, in which thetabs are separated from the strip and attached to the shells byriveting. A finished can end is achieved when the tab is fastened to theshell.

This manufacture of can ends is conventional and well known to theskilled person. It should be mentioned that the whole process isautomated with a capacity of about 2,000 ends per line per minute. Inthe beverage can industry, the production rate in general is very highand it is a continuous aim to decrease the production costs and thematerial used for can production, including the ends. Maintenance, toolchanges and other downtime should be avoided to keep costs low.

As in other areas of the food and beverage industry, the traceability ofthe manufacturing and filling of the can is important. Today, there areso-called traceability marks or markings on the cans indicating when thefilling took place and also when the main can body was manufactured.Normally, however, there is no traceability marking indicating when thefinished can ends were produced. Such markings are often required forreasons of quality. For instance, the peripheral edge of the shell mustbe precisely formed to ensure a completely tight seam against the upperflange of the can. There are also several functional requirements placedon the tab and on the attachment of the same to the shell.

Thus, there is a need for indicative markings on the tabs and the shellsas well as on the can body. The task of providing markings on the tab isespecially difficult, resulting in a demand for an improved techniquefor solving this problem.

Various attempts to provide markings of this type have been made in thepast. Indeed one has been successful when it comes to provide markingson the shell, since the shell surfaces available for markings are ratherlarge. Normally, markings of this type are provided in a stampingoperation or the like. There is, however, a general problem in usingstamping operations to provide small indicative markings on metalsurfaces, namely that these surfaces should be non-coated for acceptableresults. In some cases, however, it would be desirable to mark surfacesthat are coated with lacquer and/or paint.

When it comes to providing markings on the tab, one has not beencompletely successful due to the small tab surfaces available and thehigh requirements of elevated production rate. For material savingreasons, the modern opening tabs are quite small, inevitably leavingonly very limited tab surfaces for markings at high speed. If suchmarkings are to be provided by stamping operations or the like, the tabsurfaces must be increased. However, this calls for costly changes inthe production equipment, increases the material cost and involves arisk of non-acceptance by the consumers.

Except for the purpose of indicating the origin of the tabs, the markson the same may also be used in other contexts. In a commercial aspect,marks on the bottom surface of the tab may indicate the winner in alottery or the like. The quality requirements on such “promotional”marks are normally the same as in the cases where the origin isindicated. Further, the layout of such “promotional” marks might bechanged quite frequently, calling for frequent change of the toolingused for stamping such marks. Since such tooling is quite expensive, thecost for providing “promotional” marks can be considerable.

It is known to use laser for providing identification markings on metalsheets, see for instance U.S. Pat. No. 4,304,981. In this case, however,the markings are used for indicating defects in the manufacture of themetal strips. Thus, the requirements on the markings per se or theirpositioning are not crucial.

SUMMARY OF THE INVENTION

An object of the present invention is to eliminate the drawbacksmentioned above and to provide an improved technique for manufacturingarticles to be included in cans, which articles have distinct andindicative marks.

A further object is to provide an improved technique of marking verylimited areas on such articles.

A specific object is that the improved technique for providing markspermits high production rates.

It is also an object to provide an improved technique that allows forfrequent changes in the layout of the marks without incurring excessivecosts.

Another object is to provide an improved technique of marking sucharticles yielding satisfactory results on both non-coated and coatedsurfaces.

It is also a specific object of the invention to provide an improvedtechnique for manufacturing opening tabs for can ends, which tabs havedistinct and indicative marks.

These and other objects, which will appear from the followingdescription, have now been achieved by a method, an apparatus, anopening tab, a can end, a shell, a can and use as defined in theappended independent claims. Preferred embodiments of the invention areset forth in the subclaims.

The invention brings out several advantages. An enhanced technique ofproviding distinct markings on the article is accomplished, also whenvery limited areas are available for marking, such as on opening tabs.The new technique is suitable for high production rates required inmodern beverage can manufacturing. Further, the use of a laser unitpermits marking of both non-coated and coated surfaces. Also, the layoutof the marks can easily be changed, for example by input of a newengraving pattern to a control unit, e.g. a computer, that controls theengraving operation performed by the laser unit. Further, since astandard tab can be used, there is no need for tool change in theproduction line when no laser engravings are desired. The sameproduction line can be used in both cases, since the laser unit in thepreferred embodiment is easily disconnectible.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, presently preferred embodiments of the invention willbe described, reference being made to the accompanying schematicdrawings.

FIG. 1 illustrates the principles of a known method of manufacturing canends having opening tabs.

FIG. 2 is a side view of an apparatus according to a preferredembodiment of the invention.

FIG. 3 is a top view of an opening tab according to a preferredembodiment.

FIG. 4 is a bottom view of a tab having markings on its bottom surface.

FIG. 5 is a top view of a can end with a tab provided with the markings.

FIG. 6 is a plan view of a portion of a metal strip used for producingtabs in accordance with the invention.

FIG. 7 is schematic view of a first part of a laser unit according to apreferred embodiment of the invention.

FIG. 8 is a perspective view of a second part of a laser unit accordingto a preferred embodiment of the invention.

FIG. 9 is a plan view of a strip guiding device according to a preferredembodiment of the invention.

FIG. 10 is a cross-sectional view taken along the line X—X in FIG. 9.

FIG. 11 is an end view taken in the direction of the arrows XI—XI inFIG. 9.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a thin metal strip 1 is shown which preferably is analuminium strip having a thickness of about 0.23 mm. The strip 1 is putthrough various punching and stamping operations in a first productionstage in order to form opening rings or tabs 2 integrated with the strip1.

In another production stage, die-cut metal shells 3, preferably ofaluminium sheet having a thickness of about 0.23 mm, are put throughvarious operations for forming a can lid or end 4 which in a finalproduction stage is provided with a tab 2 which is riveted on the top ofthe shell 3.

As shown in FIGS. 3 and 4, each tab 2 has an opening 5 and a rivetportion 6. In the tab forming operations, the peripheral edge portions 2a, 2 b, 2 c are bent inwardly in a manner known per se, as shown in FIG.4. The purpose of this bending is to increase the stiffness of the tab2. Further, the tab 2 has a stiffening recess 7 on either side of theopening 5, see FIG. 3.

The finished can end 4 provided with a tab 2 riveted on the top surfaceof the shell 3 is shown in FIG. 5.

FIG. 2 shows an apparatus for the manufacture of opening tabs 2corresponding to the working of the strip shown in FIG. 1. An aluminiumstrip 1 of the type described is fed from a supply 8 to a laser unit 9supported by a supporting member 10, and finally fed to a tab formingunit 11 which is of a type known per se and which forms the tabs 2 bypunching and stamping the strip 1. The strip 1 is guided by a guidingdevice 12 when passing below the laser unit 9. The strip 1 is fed fromthe supply 8 by a feeding means 13 arranged in association with the tabforming unit 11. In the tab forming unit 11, the strip 1 is punched andstamped to form the tabs 2 integrated with the strip 1. In this type ofapparatus, the strip 1 is only intermittently fed, or indexed, into thetab forming unit 11. Thus, the feeding means 13 is activated to feed thestrip 1 after each completed stamping and punching operation in the tabforming unit 11. The feeding rate of the strip 1 and the operation ofthe laser unit 9 are controlled by a computerised control unit 14connected to the strip feeding means 13 and means (not shown) foroperating the laser unit 9. The laser unit 9, which will be describedmore in detail below, comprises a high-power and high-speed lasercapable of providing engravings in the tab surface, preferably with adepth of about 1–5 μm. This is illustrated by downwardly directed arrowsfrom the laser unit 9 in FIG. 2, corresponding to laser radiation. Thelaser unit 9 is thus arranged between the strip supply 8 and the tabforming unit 11. Between the laser unit 9 and the guiding means 12 therecan be provided means (not shown) for collecting dust produced in theengraving process. It should be pointed out that the laser unit 9 may beinstalled in a standard production line for tabs 2. The operation of thelaser unit 9 may be disconnected, in which case the tab forming line isused in a conventional manner.

The purpose of the laser unit 9 is to provide indicative, laser engravedmarkings on at least one of the upper and lower surfaces of the strip 1depending on whether markings are desired on the top surface or on thebottom surface of the tab 2, or on both these surfaces. The tab 2 shownin FIG. 3 has laser engraved marks A2, CC, 56 on its top surface,whereas the tab 2 in FIG. 4 has laser engraved marks WIN, A, 98 on itsbottom surface.

The top markings A2, CC, 56 on the tab 2 shown in FIG. 3 serve astraceability marks indicating when the tab 2 was manufactured. Thesemarks are codified in accordance with a specific system, where A2 is aweek code (A–Z=week 1–26, a–z=week 27–52), CC is an hour code (A–X=hour1–24) and 56 is a minute code (1–60). By this code system, it is exactlyindicated when the tab 2 was produced.

The bottom markings WIN, A, 98 on the tab 2 shown in FIG. 4 serve asindications of a lottery, where the mark WIN indicates that the personwho opens the can by means of the tab 2 is a winner. The other marks onthe tab A, 98 constitute an identification of the lottery in question.

In FIG. 5, the tab 2 shown in FIG. 3 is attached to the top of the shell3. Thus, the end 4 is finished and the tab 2 has traceability markingsA2, CC, 56 clearly readable for a person wishing to investigate thequality of the end 4 and/or the marked tab 2.

FIG. 6 shows a portion of the strip 1 after the laser engravingoperation, and before the tab forming unit 11. The strip portion shownin FIG. 6 basically corresponds to the position marked VI in FIG. 1. Thelaser unit 9 has engraved the markings WIN, A, 98 on one surface of thestrip 1. The approximate periphery of the tab to be produced in thefollowing tab forming steps in the unit 11 has been indicated with ghostlines in FIG. 6. In practice, the size of the laser engraved marks isabout 1.4×1.2 mm, which makes them easily readable.

In the following, the laser unit 9 will be described in some detail withreference to FIGS. 7–8. Generally, the laser unit 9 comprises a laser100, which is adapted to generate laser radiation in the form of a beamL at a suitable wavelength, and a so-called scanner head 150, which isadapted to receive the laser beam L from the laser 100, and focus anddirect the generated laser beam L to a given location S on the stripsurface. The laser 100 and the scanner head 150 are shown in FIG. 7 andFIG. 8, respectively. The requirements on the laser unit 9 are high inthe sense that the laser engraved marks must be provided in an extremelyshort time due to the high feeding rate of the strip 1. The laserradiation also has to be very accurate positioned on the strip 1, sincethe tab surface available for the markings is very small.

It is preferred that the laser 100 generates radiation in the near IRregion of approximately 1–10 μm since aluminium, normally used formanufacture of cans, exhibits high absorption of radiation in thisregion.

It is also preferred that the laser engraving operation takes placeduring the time period when the tab forming unit 11 performs a stampingand punching operation, i.e., when the strip 1 is in an immobilizedcondition. Thus, the scanner head 150 should be capable of focusing thelaser radiation to a small spot and control the position of this spot intwo dimensions on the strip surface.

Further, it is preferred that the laser 100 is capable of generatingpulsed laser radiation, since the maximum power of a laser pulse can bemany times the rated power of the laser. This will increase theengraving efficiency of the laser unit 9.

In the most preferred embodiment, shown in FIG. 7, the laser 100 is aNd:YAG laser generating radiation at 1.064 μm, and in particular a diodelaser pumped Nd:YAG laser since this laser is capable of generatinglaser radiation with good mode quality. Thus, the radiation can befocused to a minute volume producing very distinct engravings. Comparedto a conventional flash-lamp pumped Nd:YAG laser, the diode laser pumpedNd:YAG laser also has a high electrical to optical efficiency and, thus,less need for cooling.

The laser 100 of FIG. 7 outputs a laser beam L which is generated in anoptical cavity defined by a highly reflecting rear mirror 101 and apartially reflecting (R≈80%) front mirror 102. A lasing medium 103 ofNd:YAG is arranged on the optical axis OA of the cavity and issurrounded by diode lasers 104 for pumping of the medium 103. Aso-called Q-switch 105, e.g. a Pockels cell, is arranged in the cavityin a manner known per se, for generating intense lasing in a very shorttime period resulting in very high peak power laser pulses. A modeselection element 106, e.g. an iris diaphragm, is arranged within thelaser cavity to block outer portions of the laser beam L in order tooptimise its transverse mode characteristics. Thus, the laser can beforced to operate in a transverse mode that can be focused to a smallvolume, e.g. TEM₀₀. A shutter 107 is provided for blanking off the laserbeam L.

Excellent results have been achieved in practice by a modified versionof a diode laser pumped Nd:YAG laser (DynaMark T2) marketed by theGerman company IWKA. The laser emits pulses with a duration of 25 ns ina cycle time of approximately 0.1–1 μs. The average power per pulse is25 kW, with a peak pulse power of about 100 kW. This laser power isadequate for engraving colored metal surfaces, but should be increasedwhen engraving bare metal surfaces.

The scanner head 150 of FIG. 8 receives the laser beam L from the laser100 and focuses it to a small spot S on the surface of the strip 1. Thescanner head 150 comprises a telescope 151 for beam expansion, twodeflection devices 152, 153 for beam deflection, and a lens arrangement154 for beam focusing. The laser beam L is first directed through thetelescope 151 to increase the beam diameter. This will reduce the beampower per unit area to minimise damages to successive optical componentsand to optimise the beam size on the lens arrangement 154. Further, thesize of the focal spot S on the strip surface will decrease by thisprocedure.

Each deflection device 152, 153 controls the deflection of the laserbeam in one respective direction (x, y). By the combined action of thetwo deflection devices 152, 153, the laser beam L can be controlled intwo dimensions over the strip surface. The deflection devices 152, 153,as well as the laser 100, are operated by a control means (not shown)which in turn is controlled by the computerized control unit 14 (FIG.2). Preferably, the deflection devices 152, 153 are galvanometers of atype known per se, in which the rotation of a mirror 155, 156 iscontrolled by means of an electromagnetic field and feedback control.

After passing the deflection devices 152, 153 the laser beam is directedthrough the lens arrangement 154, preferably a so-called flat-fieldlens. Such a flat-field lens is designed to focus the laser beam Lperpendicular to a geometrical plane, in this case the strip surface.The focal length of the flat-field lens should be chosen with greatcare. With a large focal length, a small rotation of the mirrors 155,156 will yield a large movement of the focal spot S on the stripsurface, thereby allowing for fast displacement of the spot S. However,a too large focal length will yield a low precision in the positioningof the spot S as well as a larger spot size. A focal length of 120–180mm has been found adequate.

As shown in FIG. 4, the markings are laser engraved on the tab surfacebetween the opening 5 and the inwardly bent edge portions 2 a, 2 b and 2c provided by bending means (not shown) included in the tab forming unit11. As explained above, the laser unit 9 must be controlled veryaccurately by means of the control unit 14 in order to provide distinctlaser engraved markings on this small surface of the tab 2. Thepositioning control of the focal spot S is important. Since there is acontinuous aim to reduce the strip material used, the width of the tab 2should be as small as possible, thus leaving only a limited surface formarkings. By the high-power laser engraving according to the invention,distinct and indicative markings are provided on the tab 2 in spite ofthe small tab surface available.

The provision of laser engravings on a limited surface also calls forcareful positioning of the strip 1 during the engraving operation. Dueto the indexing motion of the strip 1 into the tab forming unit 11, thestrip 1 will swing and jump in all directions on its way from the supply8 to the tab forming unit 11. To control the position of the strip 1, aguiding device 12 is arranged in the area of the engraving operation.This guiding device 12 should allow for careful positioning of the strip1, but should not interfere with the intermittent progression of thestrip 1 into the tab forming unit 11. Preferably, the strip 1 should notbe clamped during the laser engraving operation, since this mightdisturb the indexing motion of the strip 1 or lead to stretching of thestrip 1. Also, friction must be minimized. Typically, the strip 1 shouldbe positioned with a precision of about 15 μm in the lateral, ortransverse, direction, at least when providing marks on the surface ofthe tabs 2. The vertical position of the strip 1 should also becarefully controlled within the focal region of the laser beam,typically about 0.2 mm.

In FIGS. 9–11, a strip guiding device is shown that fulfills the abovecriteria.

The guiding device 12 comprises a main block 200, an intake mechanism210, a guiding channel 220, and an outlet mechanism 240.

The intake mechanism 210 includes first and second intake rollers 211,212, each comprising a spindle 213, 214 having a number of cylindrical,laterally spaced radial projections 215, 216. The intake rollers 211,212 are arranged to receive the strip 1 with the projections 215, 216abuttingly engaging the upper and lower surfaces of the strip 1,respectively. Each spindle 213, 214 is mounted in the main block 200 forfree rotation therein. The clearance between the intake rollers 211, 212corresponds to the thickness of the strip 1 with nearly zero tolerance,in order to avoid a twisting motion of the incoming strip 1 beingtransmitted to the strip portion received in the guiding channel 220.The second spindle 214 is provided with guiding shoulders 217, 218 witha mutual distance essentially corresponding to the width of the strip 1,typically with a tolerance of about 0.5 mm.

The guiding channel 220 is defined by a guiding shoe 221, a number ofguiding elements 222, 222′ arranged in the longitudinal direction onboth sides of the channel 220, and a guiding cover 223. The distancebetween the guiding shoe 221 and the guiding cover 223 is such that thestrip 1 can move essentially without interference. An opening or window224 is defined in the cover 223 so that the strip surface is accessiblefor engraving by means of the laser unit 9. The guiding elements 222 ona first side of the channel 220 are mounted for rotation at a fixedlocation in the main block 220, whereas the guiding elements 222′ on asecond, opposite side of the channel 220 are mounted for both rotationand lateral displacement in the main block 200. Each guiding element222, 222′ comprises a rotatable guiding roller 225 which has acylindrical portion with a circumferential surface 226 for abutment onthe longitudinal edges of the strip 1 and an adjacent circumferentialshoulder 227 for defining the path of the strip 1 in the verticaldirection. The displaceable guiding elements 222′ further comprises amounting block 228, which receives the guiding roller 225 and isdisplaceably arranged on a common pin 229 extending in the longitudinaldirection of the guiding device 12. Spring-biased pusher arrangements230 are arranged to urge the guiding elements 222′ towards the firstside of the channel 220. Typically, the mounting block 228 allows for amovement of ±3 mm in the lateral direction. As an alternative (notshown), all guiding elements 222, 222′ can be displaceable and biasedtowards the center of the channel 220.

The outlet mechanism 240 corresponds to the intake mechanism 210 andwill not be further described.

The strip guiding device 12 as described above and shown in FIGS. 9–11forms a self-adjusting system for careful positioning of the strip 1during the laser engraving operation. The strip 1 is only subjected toguiding forces at its longitudinal edges. Therefore, the frictionbetween the guiding device and the strip 1 is minimal, and the indexingmovement of the strip 1 is essentially undisturbed. Another advantage isthat a large area of the strip surface can be accessible for laserengraving.

In order for the tab forming unit 11 to form each tab from the intendedportion of the strip 1 (cf. the laser-engraved areas marked by ghostlines in FIG. 6), the engraving operation should be effected as close aspossible to the tab forming operation. However, the laser unit 9 shouldpreferably be physically unconnected to the tab forming unit 11 due tothe excessive vibrations produced in the latter. Preferably, a sensor(not shown) is arranged in association with the tab forming unit 11 orthe strip feeding means 13. The sensor is adapted to indicate when thestrip 1 is in an immobilized condition, e.g., by sensing a dwellcondition of the tab forming unit 11 or the strip feeding means 13. Theoutput signal of the sensor is fed to the laser unit 9 to initiate thelaser engraving operation on the surface of the immobilized strip 1.

The laser unit 9 is disconnectible, which makes it possible to use theapparatus as a standard production line as well, even temporarily. Ifmarkings are desired on both sides of the tab 2, another laser unit (notshown) could be arranged facing the lower surface of the strip 1. Inthis case, the guiding device should be modified, by substituting theguiding shoe for a guiding cover with a window.

In one aspect of the invention, use is made of laser in the productionof opening tabs 2 to be attached to shells 3 for forming can ends 4,whereby the laser provides engravings on a metal strip 1 from which thetabs 2 are formed. The use of the laser must be carefully controlled inorder to obtain the laser engravings exactly where needed on the strip 1so as to obtain the markings exactly on the intended surface of the tab2, at high production rate.

In the illustrated embodiment, the apparatus effects the laser engravingoperation during the dwell time of the strip feeding means 13. Thisprovides for excellent control of the strip position during engraving aswell as a high production rate of laser-engraved tabs. Typically, thetab production unit 11 operates at a speed of 640 strokes/min or higher,with the strip 1 being immobilized during approximately 60 ms. In thistime, the inventive apparatus is capable of providing three laterallyspaced tab-forming strip portions with six laser-engraved letters each,the letters having a height of 2 mm (cf. FIG. 6).

This should be compared to an alternative approach of effecting theengraving operation during movement of strip (not shown). In this case,the scanner head provides for beam deflection in the lateral (x)direction only. Thus, only longitudinally spaced tab-forming stripportions can be engraved with this approach, leading to a reducedproduction rate. Further, it is more difficult to control the positionof the strip during movement thereof. In addition, the engravingoperation can only be effected while the strip is being fed at constantspeed, i.e. during approximately 15 ms when the tab production unit 11operates at a speed of 640 strokes/min. Thus, the strip feeding means 13must be capable of accelerating the strip to high speeds. However, insome cases this alternative, less preferred approach might besufficient. It should also be mentioned that a cw CO₂ laser could beused in this approach, although the focal spot S will be comparativelylarge since the laser has non-optimum mode characteristics and yieldsradiation at a longer wavelength (10.6 μm).

Finally, it should be emphasized that the invention by no means isrestricted to the embodiments described in the foregoing, andmodifications are feasible within the scope of the appended claims. Inparticular, it should be pointed out that the specific design of the canend is not crucial as long as the aimed-at laser engraved markings areprovided on the tab to be attached thereto.

It should also be mentioned that the tabs 2 could be formed in the tabforming unit 11 by other means than stamping and punching operations.

The invention could also be used for laser engraving of other articlesto be included in a can, for example the above-mentioned shell or thecan body.

1. A method of manufacturing articles to be included in cans,comprising: intermittently feeding a metal strip having an upper surfaceand a lower surface into an article forming unit; and providing at leastone of the upper surface and the lower surface of the strip with laserengravings from a laser unit when the strip is in an immobilizedcondition and before the strip is fed into the article forming unitwhere the articles are formed, said laser engravings forming marks on atleast one of the upper surface and the lower surface of the strip.
 2. Amethod as set forth in claim 1, further comprising guiding the strippast the laser unit.
 3. A method as set forth in claim 1, wherein thearticles are opening tabs to be attached to ends of the cans.
 4. Amethod as claimed in claim 1, further comprising extending the laserengravings a finite depth into a metal portion of the metal strip toform marks in at least one of the upper surface and the lower surface ofthe metal strip.
 5. A method as claimed in claim 1, wherein the strip isin the immobilized condition for less than about 60 milliseconds forforming at least four characters.
 6. A method as claimed in claim 1,wherein the upper surface of the metal strip includes a coating and thecoating is laser engraved.
 7. A method as claimed in claim 6, whereinthe laser engravings extend through the coating and into the metalstrip.
 8. A method as claimed in claim 6, wherein the articles are canends and the laser engravings are provided in the can ends fortraceability.
 9. A method as claimed in claim 1, wherein the articlesare tabs to be attached to can ends and the laser engravings includemarkings into the metal strip to indicate a person who uses a selectedone of the tabs is a winner.
 10. A method of manufacturing articles tobe included in cans, comprising: feeding a metal strip having an uppersurface and a lower surface into an article forming unit, said stripbeing fed in periods of rapid movement; and providing at least one ofthe upper surface and the lower surface of the strip with laserengravings from a laser unit when the strip is in between the periods ofrapid movement and before the strip is fed into the article forming unitwhere the articles are formed, said laser engravings forming marks on atleast one of the upper surface and the lower surface of the strip.
 11. Amethod of manufacturing opening tabs to be attached to ends of cans,comprising: intermittently moving a metal strip having an upper surfaceand a lower surface along a predetermined path into an opening tabforming unit where the opening tabs are formed; providing a laser unitalong the path at a position that precedes the opening tab forming unit;and forming laser engraved marks with the laser unit on at least aselected surface of the upper surface and the lower surface of the stripwhen the strip is in an immobilized condition, whereby the laser unit iscontrolled during immobilization of the strip such that the laserengraved marks form a distinct code on the selected surface.
 12. Amethod as set forth in claim 11, wherein the distinct code is at leastone of a code that indicates a site of production, an hour codeindicating when the tab was produced, a minute code indicating when thetab was produced, and a code that indicates that a person who opens thecan using the tab is a winner.
 13. A method of manufacturing articles tobe included in cans, comprising: intermittently feeding a metal striphaving a metal surface into an article forming unit; and providing themetal surface of the strip with laser engravings from a laser unit whenthe strip is in immobilized condition and before the strip is fed intothe article forming unit where the articles are formed, the laserengravings forming marks into the metal surface of the strip.
 14. Amethod as claimed in claim 13, further comprising: providing a coatingon the metal strip; and extending the laser engravings through thecoating and into the metal surface of the strip.
 15. An apparatus formanufacturing articles to be included in cans, comprising: a supply of ametal strip having an upper surface and a lower surface; an articleforming unit; a strip feeder between the supply and the article formingunit, the strip feeder intermittently moving the strip into the articleforming unit such that the strip is in an immobilized condition betweenperiods of intermittent movement; a laser unit arranged between thesupply of metal strip and the article forming unit, the laser unitproviding laser engravings on at least one of the upper surface and thelower surface of the strip, the laser engravings forming marks on atleast one of the upper surface and the lower surface of the strip to beformed into the articles by the article forming unit; and a control unitin communication with the laser unit, the laser unit being controlled sothat the laser engravings are provided on at least one of the uppersurface and the lower surface of the strip when the strip is in theimmobilized condition between the periods of intermittent movement. 16.An apparatus as set forth in claim 15, wherein the laser unit isarranged adjacent to the article forming unit but does not impartvibrations to or otherwise disrupt operation of the article formingunit.
 17. An apparatus as set forth in claim 15, further comprising aguide that guides said strip past said laser unit.
 18. An apparatus asset forth in claim 15, wherein the laser unit is disconnectible forallowing article manufacture without marking of the strip.
 19. Anapparatus as set forth in claim 15, wherein said articles are openingtabs to be attached to ends of the cans.
 20. An apparatus as claimed inclaim 15, wherein the metal strip has a thickness defined between theupper surface and the lower surface, and the laser engravings extendinto a metal portion of the metal strip to a depth that is within thethickness of the metal strip.
 21. An apparatus as claimed in claim 15,wherein the strip is in the immobilized condition for less than about 60milliseconds for forming at least four characters.
 22. An apparatus asclaimed in claim 15, wherein the upper surface of the metal stripincludes a coating and the coating is laser engraved.
 23. An apparatusas claimed in claim 22, wherein the laser engravings extend through thecoating and into the metal strip.
 24. An apparatus as claimed in claim22, wherein the articles are can ends and the laser engravings areprovided in the can ends for traceability.
 25. An apparatus as claimedin claim 15, wherein the articles are tabs to be attached to can endsand the laser engravings include markings into the metal strip toindicate a person who uses a selected one of the tabs is a winner. 26.An apparatus for manufacturing articles to be included in cans,comprising: a supply of a metal strip having an upper surface and lowersurface; an article forming unit; a strip feeder between the supply andthe article forming unit, the strip feeder moving the strip into thearticle forming unit in periods of rapid movement; a laser unit arrangedbetween the supply of metal strip and the article forming unit, thelaser unit providing laser engravings on at least one of the uppersurface and the lower surface of the strip, the laser engravings formingmarks on at least one of the upper surface and the lower surface of thestrip to be formed into the articles by the article forming unit; and acontrol unit in communication with the laser unit, the laser unit beingcontrolled so that the laser engravings are provided on at least one ofthe upper surface and the lower surface of the strip when the strip isbetween the periods of rapid movement.
 27. An apparatus formanufacturing opening tabs to be attached to ends of cans, comprising: asupply of a metal strip having an upper surface and a lower surface; anopening tab forming unit provided along a predetermined path followingthe supply and structured to form opening tabs; a strip feederstructured to intermittently move the strip along the path into theopening tab forming unit; a laser unit provided along the path at aposition that precedes the opening tab forming unit, the laser unitproviding laser engraved marks on at least one of the upper surface andthe lower surface of the strip; and a control unit in communication withthe laser unit, the control unit controlling the laser unit so that thelaser engraved marks are provided on at least a selected surface of theupper surface and the lower surface of the strip when the strip is inthe immobilized condition, whereby the laser unit is controlled duringimmobilization of the strip such that the laser engraved marks form adistinct code on the selected surface.
 28. An apparatus as set forth inclaim 27, wherein the distinct code is at least one of a code thatindicates a site of production, an hour code indicating when the tab wasproduced, a minute code indicating when the tab was produced, and a codethat indicates that a person who opens the can using the tab is awinner.